(A) Field of the Invention
The present invention relates to an optical pressure-sensing system and a method for sensing pressure, and more particularly, to an optical pressure-sensing system using an optical resonant cavity and a method for sensing pressure.
(B) Description of the Related Art
Many physical properties such as thermal conductivity, frictional resistance and ionization effect of gases in a chamber are properly used to measure the pressure as shown in the prior skills. U.S. Pat. No. 4,270,091 discloses a method for measuring the density of residual gases in a chamber, and more specifically, teaches exciting gases in the chamber by an electron beam, wherein the gases can generate de-excitation radiation which is proportional to the density of the excited gases in the chamber, i.e., proportional to the concentration of the residual gases in the chamber. U.S. Pat. No. 5,908,988 discloses an optical vacuum pressure gauge capable of measuring pressure between 760 to 0.1 torr. Since the reflective index of gases inside a cavity varies with pressure therein, and the reflective index can be estimated based on the phase difference between a p-polarized light and s-polarized light due to the total-internal-reflection in the cavity, the pressure or vacuum degree in the cavity can be measured from the estimated reflective index.